Note: Descriptions are shown in the official language in which they were submitted.
~1~62~8
~he present invention relates to apparatus suitable for
carrying out the periodic cleaning of electrolytic mercury
cathode cells or the like, without the necessity of opening the
cells themselves.
It is well known that for its correct operation the mercury
cathode electrolytic cell requires a periodic cleaning which
involves the stopping of the cell, its emptying, its opening, and
finally the removal, by direct intervention of the operators,
of the "mercury sludge" and of all other deposits of various
natures that, resting on the bottom of the cell, hinder the
regular flow of the mercury.
The frequency of s~ch a required cleaning varies according
to the constructional characteristics of the cell, its state of
preservation, and its operational conditions.
Moreover, between one cleaning operation and the next, a
certain number of periodic "washings" with brine in the closed
cell is employed, said washings also requiring the stopping of
the cell.
The cleaning of the cell with its attendant opening,
because of the required procedures and times, involves in prac-
tice the ollowing main disadvantages: a heavy pollution of
the environment by the mercury, a high loss of production, and
a considerable use of labor.
Thus, a main object of this invention is that of providing
an apparatus or e~uipment for cleaning the bottom of electrolytic
cells, in particular cells having mercury cathodes, and ada~ted
to achieve an efective cleaning without requiring the opening
of the cells and, thus, without polluting effects upon the
environment or work surroundings.
Still another object of this invention is that of providing
an apparatus oE the above type that is especially simple, easy
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to operate from outside the cell, and such that when not in use
it may remain in place without interfering with the regular or
normal working of the cell itself.
These, and still other ob~ects that will more clearly appear
from the detailed description that follows, are attained in
practice by an apparat~s ~or cleaniny the bottom of electrolytic
cells, particularly those having a mercury cathode, and usa~le
with closed cell, without any brine and with lifted anode packs,
said apparatus consisting essentially, according to this inven-
~- 10 tion, of-a plate or metal strap consisting of at least two crop-
ends connected to each other by a hinge or the like, and of a
total length substantially corresponding to the width of the
bottom of the cell to be cleaned, said strap being placed on the
bottom of the cell and connected to bar-like elements, preferably
rigid, protruding beyond the inlet head of the cell and connec-
table through fast connecting means (i.e., "quick-disconnect"
means) with other rigid elements so as to form rafters or struts
maneuverable from outside the cell itself, said strap, shift-
able on the bottom of the cell, being maintained in a resting
position inside the inlet head of the cell and spaced from the
bottom itself by means of spacers of electrically insulated
,~ ~ material spaced from each other to allow the regular flow of the
brine when the cell is in operation.
More partic~larly, said metal strap is so shaped as to have
a substantially trapezoidal transversal cross-section or a wedge-
like section, and is made of metal and at least partly of iron
and of a composition chemically resistant to the cell fluids.
According to the present invention, there is provided an
apparatus for cleaniny the bottom of a mercury cathode elestro-
lytic cell, by displacing the mercury sludge along said bottom ~-
while said cell is cut off from the power supply and maintained
under suction, this appara-tus comprising:
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- a metal plate displaceable along the bottom and
also capable of assuming a resting position within the inlet
- head of the cell during operation of this cell, the plate being
composed of at least two consecutively arranged sections, each of
these sections being connected to its neighboring section via
hinge means, so that the combined length of the sections constitutes
the length of the plate and is substantially coextensive with the
width of the bottom;
- at least two rigid rods for pushing the plate
along the bottom, each of these rods having one end connected
to the plate and the other end pr~ojecting beyond the inlet head
of and outside the cell, this other end adapted to be connected
via quick-connection means to extension rods so as to form
multiple-rod struts operable from outside the cell; and
- at least two supporting elements of electrically
insulated material capable of supportingthe plate while in the
resting position and of raisi~ng the plate above the bottom thereby
allowing flow of mercury and of the brine during operation of
the cell.
This invention, in a preferred embodiment, will
now be described in more detail with reference to the attached
drawings which are given for purely illustrative and not limiting
~ purposes, and in which:
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Figure 1 is a schematic perspective view of the main
elements of a chlorine-soda electrolytic mercury-cathode cell
incorporating the device of this invention;
s Figure 2 is a schematic longitudinal cross-section of the- cell of Figure 1, with mounted anode packages, including more- details and showing the cleaning device according to the present
invention;
Figure 3 is a schematic plan view of the main cleaning
element of the apparatus of this invention;
Figure 4 is a transverse cross-section of the element
represented in Figure 3; while
Figures 5 and 5a show in plan view and in cross-section,
respectively, a detail of the apparatus of the invention.
With reference to these figures, and in particular as
shown in Figures 1 and 2, an electrolytic mercury amalgam cell
for the production of chlorine and soda in general consists
essentially of a tank or cell 1 with an inlet head 2 for the
inflow of brine and an outlet head3. The inlet head 2 is, as
well known, subdivided into two compartments 4 and 5 intercom-
municatlng with each other through an aperture or channel 6 on
the bottom. Into compartment 4 is introduced the mercury, while
into compartment 5 is introduced the brine, both by conventional
means not shown. The brine passes into the cell 1 through an
aperature or channel 7 provided at or near the bottom level of
the cell in the separating wall 8 of inlet head 2.
In cell 1 are arranged the conventional anode packages 9
whose distance Erom the bottom of the cell is adjustable by any
various well known methods.
The apparatus of this invention, and s~itable for the
cleaning of the cell bottom with the closed cell at rest, con-
sists substantially of a strap or plate 10, preferably made of
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two halves connecte~ to each other through hinge 11 (Figure 3)
and of a total length that corresponds substantially to the
width of the inside of the cell 1.
The hinge 11 allows the use of a strap or plate 10 which
is not rigid but formed by the two straps, hinged together by
hinge 11, in order to provide a better fitting or adaptation of
all the plate surface to the bottom of the cell whlch bottom,
in certain cases, is not always perfectly flat, that is the
bottom not always having a level curface.
The strap 10 has a substantially trapezoidal or wedge-like
transversal cross-section (Figure 4), with a chamfered leading
edge so as to facilitate, during its shifting or movement along
the bottom of the cell from head 2 to the opposite head 3, the
detachment (by a scrapiny action) from the bottom itself of the
"mercury sludge" and any other adhering deposits that normally
accumulate thereon during the operation of such cells.
The strap 10 is preferably made of titanium or iron so as
to become magnetized and, thus, be kept closely adjacent to or
adhering to the bottom of the cell be reason of the heavy
currents that pass through it.
To the strap 10 are integrally fixed two rigid elements 12-
13, made of stainless (inox) steel or the like, whose length is
at least equal to the length (in the longitudinal direction of
the cell) of compartment 4 of inlet head 2 and which are inserted
into tubular ducts 14-15 which latter are interposed between the
two walls of compartment 4 and are suitably insulated. In this
way, the two rigid elements 12-13 throughout are guided up to
and through the outside of wall 2a (Figure 2) of the compartment
4. Said tubular ducts 14-15, during operation of the cell, are
sealed by blocks or bushings 16-17 adapted to retain and block
the ends of the rigid elements 12-13 in the wall 2a of the cell.
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Onto tllese blocks 16-17 are screwed blind flanges 1~-19 for
insuring fluid tightness of the cell.
In order to bring about the traversing or movement of the
strap 10 along the bottom of the cell, there are provlded further
rigid elements 20-21 (see Figure 3) that are screwable onto the
heads of rigid elements 12-13. These rigid elements 20 21
themselves may in their turn be extended with other similar rigid
elements (not shown) so as to form s-truts of a suEiciellt length
for displacing the cleaning strap 10 up to the opposite end of
the cell. These struts are controlled or actuated manually by
the operators from the outside of the ceLl.
Strap 10, moreover, is of such a thickness as will allow it
to pass through the rectangular port or aperture 7 provided in
the base or bottom part of wall 3 of compartment 5~ and, in
resting position, inside compartment 5. ~he strap 10, moreover,
is kept raised from the bottom of the cell by supporting elements
23 which are equally spaced under the strap and which are of a
. quadrangular shape (see Figures 5 and 5a). ~hese supporting
elements 23 are made of an electrically insulating Material and
are also corrosion-resistant, for instance they may be made of :.
ebonite~ or the like.
The cleaning operations of a cell are carried out in the
following way:
The cell is cut oE from the electric power supply and is
connected with a conventional chlorine separating plant (not
shown) which will keep the cell under suction.
After shutting down the brine-feecling valve a~ter the
electrical power cut-off, for the replacement of the chlorinated
brine contained in it, part of the brine is discharged into a
recovery tank (not shown).
~y suitable means Eor adjusting the interelectrode dis-
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tances, as conventionally provided in such cells, anodes 9 are
lited up o~t of the way to avoid that during the cleaning
operation they should come into contact with the cleaning device
arranged inside the cell and with the loosened and displaced
mercury slurry or sludge.
Thereupon the circulation of the mercury-is stopped and
flanges 18-19 are removed from the front wall of the cell, as
well as the mounting blocks 16-17 of the dcvice that were
arranged inside the cell itself. Now rigid elements 20-21 are
screwed or otherwise connected (on the inlet side of the cell
head) with the rigid elements 12-13. Successively further couples
of additional rigid elements 20-21 are added by progressively
inserting them into the cell as required, thus moving the
cleaning strap 10 along the bottom of the cell until it reaches
the opposite or outlet head 3 of the cell.
Once the cleaning operation has been completed (that is,
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after one complete forward traverse of blade 10 from left to
- right as shown in Figure 2) this latter is retracted into com-
partment 5 by the operators. The rigid elements 20-21 are then
disassembled by the operators, carrying out the inverse operation
~ of that carried out for their introduction into the cell, al-
,~ though the cell itsel is completely closed and, as well known,
is located very near to other cells in a large industrial instal-
lation.
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After having brought back the strap or blade 10 into the
~ inlet head 2 of the cell, the mercury slurry or sludge that has
,~! been pushed by the balde 10 into the outlet head 3 is removed
~ by means of a suction pump (in a well known manner) acting
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^~ through the upper cover of the outlet head 3 or through the rear
,,'f~" 30 wall of the same head 3, e.g., via conduit 3' as shown in Figure
1. Thereupon mercury is made to circulate in the cell for a
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few minutes, in consequence of which the other deposits and
incrustations already loosened from the bottom of the cell are
dragged into the outlet head 3 of the cell from which they are
removed by the operators in the usual way.
- It is sufficient to carry out this procedure just one -
single time in order to obtain a perfect cleaning of the bottom
of the cell.
After the above described operations, the cell is dis-
charged of the brine contained in it via a conventional outlet
(not shown).
Now blocks 16-17 are again mounted on the inlet head of
the cell and thereafter are re-mounted the sealing flanges 18-19.
After- this, the freshly cleaned cell may again be placed back
into normal operation.
The advantages offered by this procedure and by the device
described above are considerable. In fact, in comparison with
the traditional cleaning systems with fully opened cells, the
time necessary for carrying out the cleaning operation is
reducéd by a factor of about ten. Thus there is achieved a
very advantageous heavy reduction in the loss of production
¢ from any given cell.
S Besides this, only two operators are required for the
; cleaning of each cell, thus effecting a very significant
decrease in labor cost chargeable to the cell operation. More-
; over, and perhaps even more important, the operators will be
working under far better environmental conditions in comparison
!''' with those that occur in the conventional cleaning of fully
~ open cells. In fact, the present invention avoids the diEfusion
; of chlorine and mercury vapors into the environment, given that
the cell remains completely closed and under suction during the
entire cleaning operation. Moreover, the temperatures in the
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rooms in which the operators work are considerably lower than
those whe~e the cleaning is carried out in the conventional
manner with the cells ~ull~ open.
It has been found in practice that it is sufficient to
clean the cells with the device of the invention at time inter-
vals of even many months while still maintaining excellent oper-
ational conditions (in particular only a limited formation of
hydrogen in the cell and just a permissible percentage of sodium
in the amalgam).
According to another embodiment elso falling within the
scope of this invention, blade lO may be displaced along the
bottom of the cell by motorized means. To this end (see Figures
- 1-2), to the strap blade 10 are connected two pairs of chains
- 24-25 and 26-27, made of a suitable material conventionally
resistant to the type of corrosion encountered in the cell,
" which chains, by means of transmission wheels 28, 29, etc., are
wound up on drums or pulleys 30-31 and 32-33 driven by rever-
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' sible motor-reduction gears 34-35-36-37. By this means and with
a suitable programming o~ the action of the motors and of cor-
responding conventional limit switches (not shown), it is
possible to displace the strap lO in both direcitons, thereby
carrying out mechanically the same operations carried out by the
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operators manually as just described. It should be noted that
' for the "return cycle" of the scraper bar lO in this "motorized"
embodiment, there are included at the left end of compartment 5
;f two other transmission wheels 28' and 29' for the chains 26 and
27 that are identical in arrangemetlt ancl function to elemellts 2
and 29 as shown at the right end of compartment 5.
It is clear that to the various clescribed embodilllellts of
this invention there may be introduced modificatiolls and changes
or equivalent varaiations from the functional and structural
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point of view, without Ealling outside the scope of the inven-
tion itself. Thus, for instance, the shape and the number of
parts forming the strap 10 oE the cleaning device may be varied
just as may be varied the connection or coupling of the straps
themselves. Also the struts by which the strap is displaced
manually on the bottom of the cell may be realized in different
ways provided only that they are readily introducible and
extractable into and removable from the cells without having to
open the cells.
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